Upregulation of C/EBPβ and TSC2 by an HDAC inhibitor CG200745 protects heart from DOCA-induced hypertrophy

Endothelial cell serum and glucocorticoid regulated kinase 1 (SGK1) mediates vascular stiffening

BACKGROUND

Excessive dietary salt intake increases vascular stiffness in humans, especially in salt-sensitive populations. While we recently suggested that the endothelial sodium channel (EnNaC) contributes to salt-sensitivity related endothelial cell (EC) and arterial stiffening, mechanistic understanding remains incomplete. This study therefore aimed to explore the role of EC-serum and glucocorticoid regulated kinase 1 (SGK1), as a reported regulator of sodium channels, in EC and arterial stiffening.

METHODS AND RESULTS

A mouse model of salt sensitivity-associated vascular stiffening was produced by subcutaneous implantation of slow-release deoxycorticosterone acetate (DOCA) pellets, with salt (1 % NaCl, 0.2 % KCl) administered via drinking water. Preliminary data showed that global SGK1 deletion caused significantly decreased blood pressure (BP), EnNaC activity and aortic endothelium stiffness as compared to control mice following DOCA-salt treatment. To probe EC signaling pathways, selective deletion of EC-SGK1 was performed by cross-breeding cadherin 5-Cre mice with sgk1flox/flox mice. DOCA-salt treated control mice had significantly increased BP, EC and aortic stiffness in vivo and ex vivo, which were attenuated by EC-SGK1 deficiency. To demonstrate relevance to humans, human aortic ECs were cultured in the absence or presence of aldosterone and high salt with or without the SGK1 inhibitor, EMD638683 (10uM or 25uM). Treatment with aldosterone and high salt increased intrinsic stiffness of ECs, which was prevented by SGK1 inhibition. Further, the SGK1 inhibitor prevented aldosterone and high salt induced actin polymerization, a key mechanism in cellular stiffening.

CONCLUSION

EC-SGK1 contributes to salt-sensitivity related EC and aortic stiffening by mechanisms appearing to involve regulation of actin polymerization.

Targeting histone deacetylases for heart diseases

Histone deacetylases (HDACs) are responsible for the deacetylation of lysine residues in histone or non-histone substrates, leading to the regulation of many biological functions, such as gene transcription, translation and remodeling chromatin. Targeting HDACs for drug development is a promising way for human diseases, including cancers and heart diseases. In particular, numerous HDAC inhibitors have revealed potential clinical value for the treatment of cardiac diseases in recent years. In this review, we systematically summarize the therapeutic roles of HDAC inhibitors with different chemotypes on heart diseases. Additionally, we discuss the opportunities and challenges in developing HDAC inhibitors for the treatment of cardiac diseases.

EGCG prevents pressure overload‑induced myocardial remodeling by downregulating overexpression of HDAC5 in mice

Myocardial remodeling is a complex pathological process and its mechanism is unclear. The present study investigated whether epigallocatechin gallate (EGCG) prevents myocardial remodeling by regulating histone acetylation and explored the mechanisms underlying this effect in the heart of a mouse model of transverse aortic constriction (TAC). A TAC mouse model was created by partial thoracic aortic banding (TAB). Subsequently, TAC mice were injected with EGCG at a dose of 50 mg/kg/day for 12 weeks. The hearts of mice were collected for analysis 4, 8 and 12 weeks after TAC. Histopathological changes in the heart were observed by hematoxylin and eosin, Masson trichrome and wheat germ agglutinin staining. Protein expression levels were investigated using western blotting. Cardiac function of mice was detected by echocardiography. The level of histone acetylated lysine 27 on histone H3 (H3K27ac) first increased and then decreased in the hearts of mice at 4, 8 and 12 weeks after TAC. The expression levels of two genes associated with pathological myocardial remodeling, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), also increased initially but then decreased. The expression levels of histone deacetylase 5 (HDAC5) gradually increased in the hearts of mice at 4, 8 and 12 weeks after TAC. Furthermore, EGCG increased acetylation of H3K27ac by inhibiting HDAC5 in the heart of TAC mice treated with EGCG for 12 weeks. EGCG normalized the transcriptional activity of heart nuclear transcription factor myocyte enhancer factor 2A in TAC mice treated for 12 weeks. The low expression levels of myocardial remodeling‑associated genes (ANP and BNP) were reversed by EGCG treatment for 12 weeks in TAC mice. In addition, EGCG reversed cardiac enlargement and improved cardiac function and survival in TAC mice when treated with EGCG for 12 weeks. Modification of the HDAC5‑mediated imbalance in histone H3K27ac served a key role in pathological myocardial remodeling. The present results show that EGCG prevented and delayed myocardial remodeling in TAC mice by inhibiting HDAC5.

Function of histone methylation and acetylation modifiers in cardiac hypertrophy

Cardiac hypertrophy is an adaptive response of the heart to increased workload induced by various physiological or pathological stimuli. It is a common pathological process in multiple cardiovascular diseases, and it ultimately leads to heart failure. The development of cardiac hypertrophy is accompanied by gene expression reprogramming, a process that is largely dependent on epigenetic regulation. Histone modifications such as methylation and acetylation are dynamically regulated under cardiac stress. These consequently contribute to the pathogenesis of cardiac hypertrophy via compensatory or maladaptive transcriptome reprogramming. Histone methylation and acetylation modifiers play crucial roles in epigenetic remodeling during the pathogenesis of cardiac hypertrophy. Regulation of histone methylation and acetylation modifiers serves as a bridge between signal transduction and downstream gene reprogramming. Exploring the role of histone modifiers in cardiac hypertrophy provides novel therapeutic strategies to treat cardiac hypertrophy and heart failure. In this review, we summarize the recent advancements in functional histone methylation and acetylation modifiers in cardiac hypertrophy, with an emphasis on the underlying mechanisms and the therapeutic potential.

HDAC11 regulates expression of C/EBPβ and immunosuppressive molecules in myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSCs) constitute a heterogeneous population of immature myeloid cells derived from bone marrow and negatively regulate both innate and adaptive immunity in the tumor microenvironment. Previously we have demonstrated that MDSCs lacking histone deacetylase 11 (HDAC11) displayed an increased suppressive activity against CD8+ T-cells. However, the mechanisms of HDAC11 that contribute to the suppressive function of MDSCs remain unclear. Here, we show that arginase activity and NO production is significantly higher in HDAC11 knockout MDSCs when compared with wild-type (WT) controls. In the absence of HDAC11, elevated arginase level and enzymatic activity were observed preferentially in the tumor-infiltrated granulocytic MDSCs, whereas iNOS expression and NO production were increased in the tumor-infiltrated monocytic MDSCs. Of note and for the first time, we demonstrated an association between the elevated expression of immunosuppressive molecules with up-regulation of the transcription factor C/EBPβ in MDSCs lacking HDAC11. Interestingly, the highest expression of C/EBPβ was observed among CD11b+ Gr-1+ MDSCs isolated from tumor-bearing mice. The additional demonstration that HDAC11 is recruited to the promoter region of C/EBPβ in WT MDSCs suggests a novel molecular mechanism by which HDAC11 influence the expression of immunosuppressive molecules in MDSCs through regulation of C/EBPβ gene expression.

Histone deacetylase inhibitor CG200745 ameliorates high-fat diet-induced hypertension via inhibition of angiotensin II production

Obesity is growing rapidly worldwide due to consumption of westernized diet and lack of exercise. Obesity is one of the major risk factors of hypertension. The novel histone deacetylase (HDAC) inhibitor CG200745 was originally developed to treat various cancers. Previous studies showed that CG200745 attenuated hypertension through inhibition of cardiac hypertrophy and fibrosis in deoxycorticosterone acetate-induced hypertensive rat. The purpose of this study is to investigate the role and underlying mechanism of CG200745 in high-fat diet (HFD)-induced hypertension. Nine-week old C57BL/6 mice were fed a normal diet (ND) or HFD for 17 weeks. Each group of mice was treated with vehicle or CG200745 by intraperitoneal injection for 9 days. HFD group showed higher body weight, blood pressure (BP), HDAC activities, angiotensinogen and renin expressions in kidney, angiotensin-converting enzyme (ACE) expression in the lung, serum angiotensin II (Ang II) concentration, and myosin light chain₂₀ (MLC₂₀) phosphorylation in mesenteric artery compared with ND group. CG200745 lowered BP, HDAC activity, renin and angiotensinogen in the kidney, ACE in the lung, serum Ang II level, and phosphorylation of MLC₂₀ in HFD group. In conclusion, CG200745 ameliorated HFD-induced hypertension through inhibition of HDAC/Ang II/vascular contraction axis. Our results offer CG200745 as a novel therapeutic option for HFD-induced hypertension.

In Utero One-Carbon Metabolism Interplay and Metabolic Syndrome in Cardiovascular Disease Risk Reduction

The maternal obesogenic environment plays a role in programing the susceptibility of the fetus to postnatal non-alcoholic fatty liver disease (NAFLD), a risk factor for cardiovascular disease (CVD). NAFLD is a multisystem disease that is characterized by hepatic fat accumulation due in part to dysregulated energy metabolism network through epigenetic mechanisms such as DNA methylation. DNA methylation affects fetal programing and disease risk via regulation of gene transcription; it is affected by methyl donor nutrients such as vitamin B₁₂ , methionine, folic acid, vitamin B₆ , and choline. Although several studies have documented the role of several maternal methyl donor nutrients on obesity-induced NAFLD in offspring, currently, data are lacking on its impact on CVD risk as an endpoint. The aim of this paper is to use current knowledge to construct a postulation for the potential role of a comprehensive gestational methyl donor nutrients supplementary approach on the susceptibility of offspring to developing metabolic-syndrome-related cardiovascular complications.